In optical transceivers, an electrical signal is converted into an optical signal for transmission and an optical signal is converted into an electrical signal for reception. Japanese Unexamined Patent Publication No. 2004-297682 discloses that an optical transceiver has a plurality of processing units. Japanese Unexamined Patent Publication No. 2008-512904 discloses an optical transceiver provided with firmware. When an optical transceiver includes a plurality of processing units, for example, one processing unit of the plurality of processing units performs serial communication with an external apparatus which conducts monitoring and controlling the optical transceiver. When one processing unit communicates with the external apparatus regarding information to be processed by another processing unit of the plurality of processing units, the one processing unit needs internal communication to access another processing unit, so that a delay may be caused in communication with the external apparatus due to the time taken for the internal communication. There is concern that such a delay will hinder the optical transceiver from responding to the external apparatus within a predetermined time.